Linearly variable linear fluidic resistor

ABSTRACT

A variable linear fluid resistor in which a variable number of restricted paths connect two chambers to which the terminal fittings are connected. In addition to providing linear pressure flow characteristics, a linear relationship between rotary resistance adjusting motion and resistance is obtained.

United, States Patent Inventors Appl. No.

Filed Patented Assignee Thomas W. Bermel Corning, N.Y.; Nicholas Lazar,Scranton, Pa.

Corning Glass Works LINEARLY VARIABLE LINEAR FLUIDIC RESISTOR 18 Claims,12 Drawing Figs.

US. Cl 137/6253, 137/6253] Int. Cl Fl6k 1/52 Field otScarch 137/6253,

Primary Examiner-Arnold Rosenthal Attorneys-Clarence R. Patty, .lr.,Walter S. Zebrowski and William .1. Simmons, Jr.

ABSTRACT: A variable linear fluid resistor in which a variable number ofrestricted paths connect two chambers to which the terminal fittings areconnected. In addition to providing linear pressure flowcharacteristics, a linear relationship between rotary resistanceadjusting motion and resistance is obtained.

minnow: Hen 1625252 SHEEI 2 UF 2 FLOW PRESSURE Fig.

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ATTORNEY BACKGROUND OF THE INVENTION I. Field of the Invention Thepresent invention finds general application in the field of fluidics andmore specifically in the field of fluidic analog circuitry where linearelements are a necessity.

A fluidic resistor is a restriction which opposes fluid flow and whichcauses a pressure drop that is a function of the fluid flowingtherethrough. When such a restriction exists in the form of anelongated, small diameter tube or capillary, the flow therethrough islaminar for ratios of length to diameter between prescribed limits. Whenthe flow in such a tube is laminar, a substantially linear resistance isachieved, the magnitude thereof being approximated by theHagen-Poiseuille law 32 viscosity of the fluid (lb. f-sec./in.

L= length of resistor in.)

D inside diameter of resistor (in.)

Because of the requirement that the length to diameter ratio (or theratio of length to cross-sectional area in the case of a noncircularcross section) be maintained within prescribed limits, considerabledifficulty has been encountered in developing variable linear resistors.An additional feature of this invention, the existence of a linearrelationship between adjustment motion and resistance, has compoundeddevelop ment problems.

II. Description of the Prior Art Prior attempts at providing variablefluidic resistors have included pinching flexible tubing to reduce thecross-sectional area thereof and varying the length of a resistor tube.The latter method may be implemented by a telescoping tube or anadjustable helical path which connects two reservoirs. Since thesemethodschange the length to diameter ratio in order to changeresistance, the resultant resistors are linear only throughout a narrowrange of adjustment wherein the ratio of length to diameter satisfiesthe linearity requirement. Beyond this narrow range of adjustment, theresistance becomes nonlinear.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide a variable fluidic resistor which exhibits a linear pressureflow relationship over a wide range of resistance.

Another object of this invention is to provide a variable fluidicresistor which exhibits a linear relationship between adjustment motionand flow therethrough.

A further object of this invention is to provide a variable linearfluidic resistor.

Briefly, the variable linear fluidic resistor of this inventioncomprises first and second fluid chambers having first and secondexternal connections respectively connected thereto. A plurality ofresistive paths are connected between the first and second chambers.Means are provided for inhibiting the flow of fluid through selectedones of the plurality of resistive paths.

Additional objects, features and advantages of the present inventionwill become apparent to those skilled in the art from the followingdetailed description and the attached drawing on which, by way ofexample, only the preferred embodiments of this invention areillustrated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of apreferred embodiment of a linearly variable linear resistor inaccordance with the present invention.

FIG. 2 is a bottom plan view of the preferred embodiment.

FIG. 3 is a cross-sectional elevational view taken at lines 3- 3 of FIG.1.

FIG. 4 is a cross-sectional view taken at lines 4-4 of FIG. 3.

FIG. 5 is a cross-sectional view taken at lines 5-5 of FIG. 3.

FIG. 6 is a cross-sectional view taken at lines 6-6 of FIG. 3.

FIG. 7 is a cross-sectional view taken at lines 7-7 of FIG. 3.

FIG. 8 is a cross-sectional view taken at lines 8-8 of FIG. 3.

FIG. 9 is a schematic representation which illustrates the operation ofthe preferred embodiment.

FIG. 10 illustrates an alternative embodiment of this invention.

FIG. 11 is a pressure flow diagram for the preferred embodiment.

FIG. 12 is a graph which illustrates the relationship between flow andangular rotation of the adjusting knob for the preferred embodiment.

DETAILED DESCRIPTION Referring now to the drawings, there is shown inFIG. 3 a variable resistor comprising a main body member 10, the hollowinterior portion of which forms a cavity 12. A narrow, upwardlyextending portion 14 of the main body member 10 is externally threadedat 16. The threaded portion 16 is provided with a plurality of washersl8 and nuts 20 which are adapted to secure the variable fluidic resistorto a mounting panel.

A rotatable shaft 22 extends through the portion 14 and into the cavity12. One end of the shaft 22 is provided with a knob 24 with whichresistance adjustment can be made. Bearing surfaces for the shaft 22 areprovided by a bore 28 in the member 10 and a brass bearing 26 which issituated in the end of the extended portion 14. The extended portion 14contains a bore 40, one end of which is inwardly tapered to form an O-ring seat 38. The shaft 22.is provided with two flanged portions 30 and32. A seal is effected between the shaft and the housing 10 by twoO-rings 34 and 36, the O-ring 34 being disposed between the O-ring seat38 and the flanged portion 30, and the O-ring 36 being disposed betweenthe flanged portions 30 and 32. A spring 42 is disposed between theflanged portion 32 and the bearing 26, thereby compressing the O-ring 34between the flanged portion 30 and the O-ring seat 38.

When assembling the heretofore described subassembly, the O-rings 34 and36 are mounted in their indicated positions, and the spring 42 and thebearing 26 are inserted over the shaft. The bearing 26 is forced againstthe spring 42 until the bearing reaches the position shown in FIG. 3,and the end of the extended portion 14 is then crimped inwardly toretain the bearing 26.

In accordance with this invention a variable number of restricted pathsor resistors are connected between two end chambers. The restricted pathhousing is shown in FIG. 3 to include four laminated plates 44, 46, 48and 50 which are etched, machined or otherwise provided with passages orchannels which will be hereinafter described. The plates 44, 46, 48 and50 are shown in FIGS. 2,4,5 and 6, respectively, to contain four holes52 which are equally spaced around the periphery thereof and which arealigned with four internally threaded holes 54 in the main body member10. Four screws 56 pass through the holes 52 and engage the threadedholes 54 to secure the plates 44, 46, 48 and 50 to the member 10. Agasket 59 which is interposed between the plate 50 and the member I0provides a fluidtight seal therebetween. It may be desirable to adhereadjacent plates to each other to a greater extent than that provided bytightening the screws 56. This may be accomplished by fusing, gluing orotherwise securing adjacent plates to each other.

As shown in FIG. 6 the plate 50 contains two rows of holes 58 and 60which extend entirely therethrough, each row being situated on acircular path. Each of the holes 60 commu- 'nicates with a correspondingchannel 62 in the surface of the plate 48 (see FIG. 5). The remainingends of the channels 62 communicate with a chamber 64. Each of the holes58 in the plate 50 is aligned with a corresponding hole 66 which extendsentirely through the plate 48 and communicates with a correspondingchannel 68 in the surface of the plate 46 (see FIG. 4). The remainingends of the channels 68 communicate with a chamber 70. An externalconnection fitting 72 is aligned with a hole 74 which extends throughthe plate 44 and communicates with the chambers 64 and 70. Anotherexternal connection fitting 76 communicates with the holes 78, 80, 82and 84 which extend through the plates 44, 46, 48 and 50, respectively.

A disk 87 having a rectangular hole therethrough is mounted on the endportion 88 of the shaft 22 which has a rectangular cross section. Thedisk 87 has an enlarged hub 86. A flange 90 extends 180 around thecircumference of the disk 87. A screw 92, which extends through thesidewall of the main body member 10, is adapted to engage the sides ofthe flange 90 and thereby limit the rotation of the disk 87 is slightlyless than 180. The flange 90 may extend more or less than theillustrated amount depending on the desired amount of shaft rotation.Situated adjacent the disk 87 is a circular plate 94 having anoncircular hole therethrough into which extends a correspondinglyshaped protrusion of the hub 86. An annularly shaped slot 96 extends 180around the surface of the plate 94 adjacent the plate 50. The matingsurfaces of the plates 50 and 94 are polished to provide a substantiallyfluidtight interface. A spring 98 which surrounds a portion of the shaft22 bears against the disk 87 to cause the plate 94 to bear tightlyagainst the plate 50.

The operation of the disclosed embodiment will now be described,reference being made to the schematic illustration of FIG. 9. As statedhereinabove, the present invention basically consists of two endchambers which are connected by a variable number of linear resistorchannels. In FIG. 3, one of these end chambers is shown to consist ofthe combination of the chambers 64 and 70, the other end chamberconsisting of the slot 96 in the circular plate 94. The externalconnection fittings 72 and 76 respectively communicate with these twoend chambers. A first series of resistive paths which may connect thetwo end chambers consists of the channels 68, the holes 66 and the holes58. A second series of resistive paths which may connect these endchambers consists of the channels 62 and the holes 60. All of theabove-defined resistive paths are equal in length, and each pathprovides a predetermined linear resistance. The cross-sectional area ofthe holes 58, 60 and 66 is greater than that of the resistive channels62 and 68, the holes therefore contributing only a negligible amount ofresistance.

FIG. 9 illustrates how any number of resistive paths may be selected toconnect the slot 94 with the chambers 64 and 70. When the shaft 22 isrotated between its maximum limits of rotation, the slot 96 is inconstant communication with the hole 84. The position of the slot 96 asillustrated in FIG. 9 connects eight resistive paths in parallel. As theshaft is rotated and the slot moves to a new position, the holes 58 and60 are alternately cut by the end of the slot. The primary purpose forproviding a plurality of rows of holes is to permit the end of the slotto cut through one hole at the time, two holes never beingsimultaneously partially open there must always be a space betweenadjacent holes in each row to provide mechanical strength. if only onerow of holes were used, the inter hole spacing would cause a dead spotin the rotation of the plate 94 during which time there would be nochange in resistance. The provision of a plurality of rows of holespermits the slot 96 to cut one hole in one row and then immediately cutone hole in another row, no dead spots being encountered between thesetwo holes.

The plates 44, 46, 48, 50 and 94 may be formed of any suitable materialsuch as metal, glass, ceramic, plastic, or the like, and may be secured,sealed or bonded together by any suitable method well known to onefamiliar with the art, such as fusion of the plates, securing the plateswith screws, and the like. The plates may be machined, etched orotherwise grooved to provide the openings, holes and channels throughwhich the fluid passes. This invention is not limited to any particularfluid and may be used in systems employing such compressible fluids asair, nitrogen or other gases, or incompressible fluids as water or otherliquids.

The main body member may be constructed from any suitable material suchas plastic, ceramic, metal or the like, which provides adequate strengthin the thin-walled extended portion 14. The disk 87 is preferablyconstructed from metal since high stresses are incurred when the flangedportion 90 contacts the limit screw 92.

One variable resistor constructed in accordance with the presentinvention contained three circular rows of holes in the top plate 50.One of the rows contained ll holes, and the other two contained 10 holeseach. A 93 rotation of the shaft 22 was required to vary the resistancefrom zero to a maximum value. Therefore, each 3 of rotation permittedthe slot 96 to communicate with one additional hole. It is obvious thatsince there were three rows of holes in the top plate, three plateshaving resistor channels therein were required rather than the twoplates shown in the preferred embodiment.

The circular plate 94 could be replaced by a semicircular disk 100 whichis shown in H0. 10. Such a disk covers all of the holes 58 and 60 exceptthose which are to be used as resistive paths. When the disk 100 isused. the cavity 12 takes the place of the slot 96. Thus, fluid issuingfrom the hole 84 would enter the cavity 12 and thereafter flow into theexposed ones ofthe holes 58 and 60. Since this alternative embodimenthas an increased capacitance due to the size of the cavity 12, theslotted plate 94 is preferred over the disk [00 in systems wherein suchcapacitance is undesirable.

FIGS. 10 and 11 are graphs which illustrate the performance of thelinearly variable linear resistor of this invention. For every value ofresistance to which this resistor may be adjusted, the pressure flowcharacteristics are linear as illustrated in FIG. 11 since each of theresistive paths consists of a linear resistor.

As illustrated in FIG. 12 the relationship between flow and angularrotation of the shaft 22 is also substantially linear. Each increment ofangular adjustment adds or subtracts an equal increment of resistance,thereby causing a minute step increase or decrease in the flow throughthe resistor.

A nonlinear relationship between angular rotation and flow may beachieved by providing nonequal resistive paths of different lengths orcross-sectional areas.

This invention is not limited to the circularly arranged holes describedin the preferred embodiment. The holes could lie on a curve such as aspiral, a straight line or the like so long as the means which inhibitsfluid flow through the holes is provided with the proper motion.Furthermore, the holes do not necessarily connect to resistive pathswhich are perpendicular thereto. Rather, the holes could themselves beresistive paths which linearly extend between the two end chambers.

We claim:

1. A variable linear fluidic resistor comprising first and secondchambers,

first and second fluid coupling means respectively connected to saidfirst and second chambers,

a plurality of linear resistive paths connected between said first andsecond chambers, the length and the cross-sectional area of each linearresistive path being such that the flow of fluid therethrough issubstantially laminar and the ratio of the fluid flow through saidlinear resistive paths to the pressure difi'erential thereacross issubstantially constant, and

means for inhibiting the flow of fluid through selected ones ofsaidplurality ofresistive paths.

2. A variable linear fluidic resistor in accordance with claim 1 whereinsaid resistive paths are connected to a first surface which defines onewall of said first chamber.

3. A variable linear fluidic resistor in accordance with claim 2 whichfurther comprises a movable member having a slot therein, the sidewallsof said slot communicating with said first surface to provide afluidtight seal, said slot and the portion of said first surfaceintercepted by said slot forming said first chamber.

4. A variable linear fluidic resistor in accordance with claim 3 whereinsaid movable member is rotatable.

5. A variable linear fluidic resistor in accordance with claim 3 whereinsaid first fluid coupling means communicates with a hole whichterminates on said first surface within said first chamber.

6. A variable linear fluidic resistor in accordance with claim 5 whereinsaid slot is annularly shaped and said resistive path terminations arelocated on a circular path.

7. A variable linear fluidic resistor in accordance with claim 6 whereinsaid first surface is one of the surfaces of a first flat plate, saidresistor further comprising at least one resistor plate adjacent thesurface of said first flat plate which is opposite said first chamber,the surface of each said resistor plate having a plurality of channelstherein, and a plurality of holes in said first plate communicating withone end of each of said channels, the remaining ends of said channelsterminating at said second chamber.

8. A variable linear fluidic resistor in accordance with claim 2 whereinsaid inhibiting means comprises a flat movable member which is situatedwithin said first cavity on said first surface and which is adapted tocover any number of resistive terminations.

9. A variable linear fluidic resistor in accordance with claim 8 whereinsaid flat movable member is a rotatable semicircular disk and saidresistive terminations lie on a circular path.

110. A variable linear fluidic resistor comprising a first flat platehaving first and second surfaces,

first means disposed adjacent the first surface of said first plate toform a first chamber,

at least one resistor plate disposed adjacent to the second surface ofsaid flat plate, each said resistor plate having a plurality of channelsin one surface thereof, each of said channels providing a linearresistance to the flow of fluid therethrough,

a plurality of holes connecting a first end of each of said channels tothe first surface of said flat plate, the resistance of said holes tothe flow of fluid being negligible in comparison to the resistance ofsaid plurality of channels,

a second chamber, the second ends of each of said channels terminatingat said second chamber,

first and second external connectors respectively connected to first andsecond chambers, and

means for inhibiting the flow of fluid through selected ones of saidplurality of channels.

11. A variable linear fluidic resistor in accordance with claim 10wherein said means for inhibiting comprises a movable member havingfirst and second surfaces, the first surface of said movable memberdisposed adjacent the first surface of said flat plate,

a slot in the first surface of said movable member, said slot beingadapted to engage any number said plurality of holes in the firstsurface of said flat plate,

said slot and the portion of the first surface of said flat plate whichis intercepted by said slot forming said first chamber, and

a main hole through said flat plate which terminates on the firstsurface thereof within said first chamber, said first external connectorcommunicating with said main hole.

112. A variable linear fluidic resistor in accordance with claim 11which further includes means to rotate said movable member.

13. A variable linear fluidic resistor in accordance with claim 12 whichfurther includes means to force the first surface of said movable memberagainst the first surface of said flat plate to form a substantiallyfluidtight interface therebetween.

M. A variable linear fluidic resistor in accordance with claim 13 whichfurther includes means to limit the extent of rotation of said movablemember.

B5. A variable linear fluidic resistor comprising a first flat platehaving first and second surfaces,

a hollow member disposed adjacent the first surface of said first plate,a substantially fluidtight cavity being formed by said hollow member andsaid first plate,

a bore through said hollow member opposite said first plate,

a shaft extending through said bore,

means for providing a substantially fluidtight seal between said shaftand said hollow member, at least one resistor plate disposed ad acent tothe second surface of said flat plate, each said resistor plate having aplurality of channels in one surface thereof,

a plurality of holes connecting a first end of each of said channels tothe first surface of said first plate,

a first chamber, the second ends of each of said channels terminating atsaid first chamber,

a first external connector communicating with said first chamber,

a movable plate having first and second surfaces, the first surface ofsaid movable plate disposed adjacent the first surface of said firstplate,

a slot in the first surface of said movable plate, said slot beingadapted to engage any number of said plurality of holes in the firstsurface of said first plate, said slot and the portion of the firstsurface of said first plate which is intercepted by said slot forming asubstantially fluidtight chamber,

a main hole through said flat plate which terminates on the firstsurface thereof within said fluidtight chamber,

a second external connector communicating with said main hole, and

means for connecting the end of said shaft which extends into saidcavity to said movable plate.

16. A variable linear fluidic resistor in accordance with claim llSwhich further includes means to limit the extent of rotation of saidmovable member.

17. A variable linear fluidic resistor in accordance with claim 16 whichfurther includes means to force the first surface of said movable plateagainst the first surface of said first plate.

18. A variable linear fluidic resistor in accordance with claim 1wherein the cross-sectional area of said linear resistive paths issubstantially constant throughout the lengths thereof.

1. A variable linear fluidic resistor comprising first and secondchambers, first and seconD fluid coupling means respectively connectedto said first and second chambers, a plurality of linear resistive pathsconnected between said first and second chambers, the length and thecross-sectional area of each linear resistive path being such that theflow of fluid therethrough is substantially laminar and the ratio of thefluid flow through said linear resistive paths to the pressuredifferential thereacross is substantially constant, and means forinhibiting the flow of fluid through selected ones of said plurality ofresistive paths.
 2. A variable linear fluidic resistor in accordancewith claim 1 wherein said resistive paths are connected to a firstsurface which defines one wall of said first chamber.
 3. A variablelinear fluidic resistor in accordance with claim 2 which furthercomprises a movable member having a slot therein, the sidewalls of saidslot communicating with said first surface to provide a fluid tightseal, said slot and the portion of said first surface intercepted bysaid slot forming said first chamber.
 4. A variable linear fluidicresistor in accordance with claim 3 wherein said movable member isrotatable.
 5. A variable linear fluidic resistor in accordance withclaim 3 wherein said first fluid coupling means communicates with a holewhich terminates on said first surface within said first chamber.
 6. Avariable linear fluidic resistor in accordance with claim 5 wherein saidslot is annularly shaped and said resistive path terminations arelocated on a circular path.
 7. A variable linear fluidic resistor inaccordance with claim 6 wherein said first surface is one of thesurfaces of a first flat plate, said resistor further comprising atleast one resistor plate adjacent the surface of said first flat platewhich is opposite said first chamber, the surface of each said resistorplate having a plurality of channels therein, and a plurality of holesin said first plate communicating with one end of each of said channels,the remaining ends of said channels terminating at said second chamber.8. A variable linear fluidic resistor in accordance with claim 2 whereinsaid inhibiting means comprises a flat movable member which is situatedwithin said first cavity on said first surface and which is adapted tocover any number of resistive terminations.
 9. A variable linear fluidicresistor in accordance with claim 8 wherein said flat movable member isa rotatable semicircular disk and said resistive terminations lie on acircular path.
 10. A variable linear fluidic resistor comprising a firstflat plate having first and second surfaces, first means disposedadjacent the first surface of said first plate to form a first chamber,at least one resistor plate disposed adjacent to the second surface ofsaid flat plate, each said resistor plate having a plurality of channelsin one surface thereof, each of said channels providing a linearresistance to the flow of fluid therethrough, a plurality of holesconnecting a first end of each of said channels to the first surface ofsaid flat plate, the resistance of said holes to the flow of fluid beingnegligible in comparison to the resistance of said plurality ofchannels, a second chamber, the second ends of each of said channelsterminating at said second chamber, first and second external connectorsrespectively connected to first and second chambers, and means forinhibiting the flow of fluid through selected ones of said plurality ofchannels.
 11. A variable linear fluidic resistor in accordance withclaim 10 wherein said means for inhibiting comprises a movable memberhaving first and second surfaces, the first surface of said movablemember disposed adjacent the first surface of said flat plate, a slot inthe first surface of said movable member, said slot being adapted toengage any number said plurality of holes in the first surface of saidflat plate, said slot and the portion of the first surface of said Flatplate which is intercepted by said slot forming said first chamber, anda main hole through said flat plate which terminates on the firstsurface thereof within said first chamber, said first external connectorcommunicating with said main hole.
 12. A variable linear fluidicresistor in accordance with claim 11 which further includes means torotate said movable member.
 13. A variable linear fluidic resistor inaccordance with claim 12 which further includes means to force the firstsurface of said movable member against the first surface of said flatplate to form a substantially fluidtight interface therebetween.
 14. Avariable linear fluidic resistor in accordance with claim 13 whichfurther includes means to limit the extent of rotation of said movablemember.
 15. A variable linear fluidic resistor comprising a first flatplate having first and second surfaces, a hollow member disposedadjacent the first surface of said first plate, a substantiallyfluidtight cavity being formed by said hollow member and said firstplate, a bore through said hollow member opposite said first plate, ashaft extending through said bore, means for providing a substantiallyfluidtight seal between said shaft and said hollow member, at least oneresistor plate disposed adjacent to the second surface of said flatplate, each said resistor plate having a plurality of channels in onesurface thereof, a plurality of holes connecting a first end of each ofsaid channels to the first surface of said first plate, a first chamber,the second ends of each of said channels terminating at said firstchamber, a first external connector communicating with said firstchamber, a movable plate having first and second surfaces, the firstsurface of said movable plate disposed adjacent the first surface ofsaid first plate, a slot in the first surface of said movable plate,said slot being adapted to engage any number of said plurality of holesin the first surface of said first plate, said slot and the portion ofthe first surface of said first plate which is intercepted by said slotforming a substantially fluidtight chamber, a main hole through saidflat plate which terminates on the first surface thereof within saidfluidtight chamber, a second external connector communicating with saidmain hole, and means for connecting the end of said shaft which extendsinto said cavity to said movable plate.
 16. A variable linear fluidicresistor in accordance with claim 15 which further includes means tolimit the extent of rotation of said movable member.
 17. A variablelinear fluidic resistor in accordance with claim 16 which furtherincludes means to force the first surface of said movable plate againstthe first surface of said first plate.
 18. A variable linear fluidicresistor in accordance with claim 1 wherein the cross-sectional area ofsaid linear resistive paths is substantially constant throughout thelengths thereof.